The present invention relates to the field of hydraulics. More particularly, this invention relates to a tandem fixed displacement pump with a torque control circuit associated therewith.
Tandem fixed displacement pumps in general are well known in the hydraulic art. Tandem fixed displacement pumps can be useful in an open circuit arrangement where they supply pressurized fluid to two different load circuits while being driven by a single source of rotary power or driveline. For example, one of the pumps of a tandem fixed displacement pump can be used to operate the loader bucket (boom and tilt functions) on a small utility tractor or skid steer loader and the other pump can be used to operate various "high flow" attachments, including but not limited to road planers, brush cutters, or post hole augers.
Due to a variety of potentially constraining factors, including but not limited to engine size, couplings, and input shaft strength, there is a limited torque capacity available to the tandem fixed displacement pump. Problems can result when high pressure is demanded by both of the load circuits at the same time. Some means and method of coordinating the pressure requirements in each of the load circuits would be desirable to reduce the input torque required so that it does not exceed the maximum allowable torque.
Therefore, a primary objective of the present invention is the provision of a tandem fixed displacement pump with a torque control circuit that keeps the available torque capacity from being exceeded.
Another objective of this invention is the provision of a tandem fixed displacement pump system that provides priority pressure to a primary (high flow) load circuit and a secondary flow to a second load circuit when the available torque of the driveline permits.
Another objective of this invention is the provision of a tandem fixed displacement pump with torque control that is economical to manufacture, simple to adjust, reliable, and durable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims that follow.